This invention relates to a package structure for supporting a semiconductor device and, more particularly, to a package for supporting a semiconductor device comprising a package wall through which an accurate position of the semiconductor device is to be determined.
Recent progress in the field of semiconductor devices for infrared detectors has been significant. Particularly, detectors using a silicon Schottky barrier type semiconductor device for monitoring the wavelength range of from 3 to 5 .mu.m can be realized with a monolithic two dimensional detector having 512.times.512 image pixels providing a superior image.
Most silicon Schottky barrier type infrared detectors are designed to receive incoming infrared rays at a silicon substrate surface which is the bottom or back of the semiconductor device, on the opposite side of the substrate from the surface on which the semiconductor element is formed. The infrared rays are photoelectrically converted into an electric current at the Schottky barrier in the semiconductor element on the face side of the semiconductor device.
FIG. 1 illustrates in cross section one example of a known semiconductor device 1 which can be contained within a package for use as a semiconductor infrared ray detector. It is seen that the semiconductor device 1 comprises a silicon substrate 2 and a semiconductor element 3, including inter alia a Schottky barrier 4, formed on the silicon substrate 2. Thus, the semiconductor device 1 has a first major surface 5 which is defined by the upper surface of the semiconductor element 3 and a second major surface 6 which is defined by the bottom surface of the silicon substrate 2. While not seen from FIG. 1, the semiconductor device 1 is substantially rectangular in plan and has four corners as seen in FIG. 2 which will be described later. The semiconductor device 1 receives incident infrared rays from the second major surface 6 as shown by an arrow 7.
In FIGS. 2 and 3, it is seen that the semiconductor device 1 shown in FIG. 1 is mounted within a package 8 for an infrared ray detector. The package 8 is a substantially box-shaped container having a main body 9 with a rectangular top wall 10, four side walls 11 and a cover plate 12. The top wall 10 is provided with a rectangular exposure window 13 which has length and width dimensions smaller than those of the rectangular semiconductor device 1. The semiconductor device 1 is attached at the periphery of its back face or the second major surface 6 to the inner surface of the package top wall 10. Accordingly, a substantial portion of the central area of the second major surface 6 of the semiconductor device 1 is exposed through the exposure window 13, so that the second major surface 6 which is the surface of the semiconductor device 1 for receiving infrared rays, can be irradiated by the infrared rays to be monitored.
With the above described conventional package structure for a semiconductor device, the semiconductor device 1 is mounted within the package 8 so that the second major surface 6, which is the back face of the semiconductor device 1, is exposed through the exposure window 13 formed in the package 8. However, semiconductor element 3 on the face side of the device 1 cannot be detected through the exposure window 13. Therefore, the exact position of the semiconductor device 1 cannot be determined from the infrared ray receiving side of the package 8, making it very difficult to precisely position a spectral filter or a cooler on the infrared ray receiving side of the package 8 with respect to the detector element such as the Schottky barrier 4 of the semiconductor device 1.
Thus, with the package structure of the conventional design, when it is necessary to position a cooler on the back side or the second major surface 6 of the semiconductor device 1 with respect to the infrared ray detecting element 4 on the first major surface 5 of the semiconductor device 1, a position indicating mark must be provided on the back side or the second major surface 6 of the semiconductor device 1 in relation to the infrared ray detecting element 4 on the first major surface 5. This complicates the manufacture of the semiconductor infrared detector. Further, in the infrared ray detector such as the two-dimensional detector in which the area of the infrared ray detecting element 4 is large and extends over substantially the entirety of the semiconductor element 3, it has been necessary to arrange the above-mentioned position indicating mark so as to have no optical influence on the detection of infrared rays.